1. Field of the Invention
The present invention relates to a heat-assisted magnetic recording head capable of a high-density recording, and more particularly, to a light delivery module that can be fabricated in an integrated fashion while providing an enhanced near-field, and a heat-assisted magnetic recording head using the light delivery module.
2. Description of the Related Art
In the field of the magnetic recording heads, research on high-density magnetic recording continues. A recording density of 100 Gbit/in2 has been achieved in a longitudinal magnetic recording, and a recording density of 100 Gbit/in2 or more may be possible in a perpendicular magnetic recording. However, the magnetic recording technology has a limitation in providing a high recording density because of a thermal instability of recording bit due to a super paramagnetic effect.
A thermal stability in a recoding medium is determined by a ratio of magnetic anisotropy energy to thermal energy. To increase the magnetic anisotropy energy, a magnetic recording medium must be formed of a material with a strong coercive force. When the magnetic recording medium is formed of a material with a high coercive force, a correspondingly high magnetic field is required for recording. However, since the magnetic field is saturated to a predetermined level at a tip portion of a small-sized recording head for improving a recording density, a generated magnetic field has a limited strength and thus recording is impossible.
To solve this problem, a heat-assisted magnetic recording (HAMR) method has been under development. In the HAMR method, the coercive force of the corresponding position is temporarily decreased by heating a local portion of the recoding medium above the Curie temperature. When compared to the related art magnetic recording method, the HAMR method can further reduce the strength of a magnetic field required for recording.
At this point, since a region on which the data is recorded is heated above the Curie temperature, the recording density is determined by the width of the heated portion, not by the size of a pole generating a magnetic field in a gap. For example, when a heating unit is a laser diode, a data recording density is determined by the spot size of a laser light emitted from the laser diode. Accordingly, an optical unit for reducing the size of a light spot and providing a high-intensity light is required.
FIG. 1 is a view of an example of a related art HAMR head. Referring to FIG. 1, an HAMR head 22 includes a magnetic recording unit 24, a light source 52 heating a magnetic recoding medium 16, and a light delivery module 26 delivering the light from the light source 52 to the magnetic recording medium 16.
The magnetic recording unit 24 includes a coil 33 generating a magnetic field for recording, a recording pole 30 applying the magnetic field to the magnetic recording medium 16, and a return yoke 32 magnetically connected to the recording pole 30 to form a magnetic path H. The recording pole 30 includes a first layer 46 and a second layer 48.
The light delivery module 26 includes an optical waveguide 50 delivering light emitted from the light source 31, and an optical fiber 54 connecting the light source 52 to the optical waveguide 50. Light energy is delivered to the magnetic recording medium 16 through a heat discharge surface 56 formed on one end of the optical waveguide 50. Accordingly, a predetermined portion of the recording medium 16 is heated and its coercive force is reduced.
The magnetic recording medium 16 relatively moves in a direction of an arrow A with respect to the HAMR head 22. Accordingly, the heated portion of the magnetic recording medium 16 is positioned on the recording pole 30 through the relative motion. Accordingly, the recording pole 30 can easily perform a magnetic recording operation on the heated portion. The heated portion of the magnetic recording medium 16 is cooled after the magnetic recording operation. Accordingly, the cooled portion of the magnetic recording medium 16 restores the original strong coercive force and thus maintains a thermally-stable recording bit.
To perform the high-density recording through the HAMR head, the light spot must be able to sufficiently heat the magnetic recording medium while being small in size. However, this structure cannot provide a field enhancement effect. Moreover, the optical waveguide must be fabricated separately from the magnetic head and must be precisely aligned.
Additionally, a focused ion beam (FIB) process, which is accompanied by a nano aperture process for field enhancement, is low in resolution. This causes a process error, leading to deterioration of the field enhancement characteristics.